Almost 2000 Vodafone customers ‘open to fraud’ after personal details were accessed.

Vodafone Group Plc. said criminals accessed customer account details, including phone numbers and some bank details, in the second hacking attack in just over a week on a U.K. phone carrier.The telecommunications company said that criminals used customer details from an ‘unknown source’ to access the accounts of 1,827 customers between Wednesday and Thursday this week. Though the names and bank details of some customers may be in the hands of the criminals, Vodafone said an investigation and ‘mitigating actions’ had limited the damage to a ‘handful’ of customers. The hackers accessed subscribers’ e-mail addresses and passwords through a third party and Newbury, England-based Vodafone’s own systems weren’t breached, the company said.

On Friday, the company notified the National Crime Agency and Information Commissioners’ Office, which is responsible for guarding personal data privacy in the U.K. Police have arrested two teenage boys in connection with the probe into the hack, which may have exposed fewer than 21,000 unique bank account numbers.

At the time of the TalkTalk incident, Vodafone said it has a team of security experts that monitor the status of its network and computer systems “continuously” to keep customer data safe. Adultery website AshleyMadison.com was hit in July, and the perpetrators ended up releasing information they said included details of more than 36 million users including full names, e-mails and banking information.